As the optical fields for optical communications, optical disks, displays, optical sensors, and the like dramatically develop, achieving both performance and cost becomes important for optical resin materials. Expectations for transparent resin materials which are easy to process become large in fields of biochips, micro reactors, and the like, in lieu of glasses. In all fields, processing of a base material surface, in particular, microprocessing becomes requisite, and the microprocessing becomes an important technology in a recent semiconductor field where integration becomes remarkable. Conventionally, to form a minute pattern on the surface of a transparent material, schemes of cutting the surface mechanically or of printing a pattern using a resist, a thermo, ultraviolet, or electron radiation curing resin, or the like are used. In particular, to cope up with the present trend and future need for miniaturization of various devices, several different patterning methods are under continuing development. Injection molding has its limitation below 500 μm of film thickness. However, various advanced devices including anti reflecting film or coating requires patterning on a sheet or a film with thickness much below the limit of injection molding.
According to the mechanical cutting, however, there is a problem such that an advanced and complex processing technique is required. According to the pattern printing using a resist or the like, steps thereof are complicated, and there is a problem in the durability, such as peeling of a printed pattern. Further, as patterns become minuter, a mechanism which controls a whole process highly precisely becomes requisite, so that the cost issue becomes not negligible.
To cope with such problems, there is proposed a thermal imprint method for forming a minute pattern at low cost. That is, this is a method of pressing a mold, having a minute pattern heated more than or equal to a glass transition temperature of a resin, against a resin substrate, and of transferring the minute pattern of the mold on the melted resin surface.
Disclosed so far to improve the thermal imprint characteristics (transferability, mold release characteristic, and the like) and the productivity (throughput) are a scheme of providing an insulator to shorten a cycle of temperature rising and cooling (see, for example, Japanese Unexamined Patent Application Laid-open Publication No. 2002-361500), and a scheme of providing an ultrasonic generation mechanism to reduce the melt viscosity by ultrasonic (see, for example, Japanese Unexamined Patent Application Laid-open Publication no. 2004-288811). However, there are few literatures which mentioned materials used for thermal imprint, and development of the materials for thermal imprint is desired.
In general, examples of materials used for thermal imprint are resin materials, glasses, metals, and the like. The resin materials can be molded at a lower temperature in comparison with imprinting to metals or glasses, thus advantageous for the manufacturing cost.
An example of resins is a (meta) acrylic resin represented by polymethacrylic acid (PMMA) or a polycarbonate resin, but have a problem such that the heat resistance is low and size distortion occurs due to water absorption. Further, controlling a balance between the fluidity and the solidification is difficult, so that it is difficult to maintain and use a minutely-transferred pattern (see, for example, Japanese Unexamined Patent Application Laid-open Publication No. 2000-158532).
On the other hand, as a resin having both heat resistance and dimension stability originating from the low water absorption coefficient, there are cyclic-olefin-based thermoplastic resins. In general, the cyclic-olefin-based thermoplastic resins are superior in the transparency, the chemical resistance property, and the low moisture absorption characteristic, and its heat resistance can be easily controlled by the structure of the cyclic-olefin or the contained amount of the cyclic-olefin in the resin. The resin has a low viscosity, and a short relaxation time (time necessary for filling the resin in the pattern of a mold), and is less adhered to the mold, and is superior in the transfer accuracy of a minute pattern, so that application as a thermal imprint material is expected as having a good productivity (see, for example, J. Mater. Chem., 2000, volume 10, page 2634).
See also, Nanoimprint Lithography in Topas, a highly UV-transparent and chemically resistant thermoplast, T. Nielsen, D. Nilsson, et al.